Auger electron spectroscopy study of the surface segregation in silver–palladium alloys

Reniers, François; Jardinier‐Offergeld, M.; Bouillon, Florent

doi:10.1002/sia.740170609

Cited by 14 publications

(4 citation statements)

References 35 publications

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“…Moreover, from the O KLL peak, we could see that compared with silver concentration, concentrations of palladium and oxygen relatively increased. For the sample before thermal treatment (sample b), the Ag/Pd ratio was about 1:2.5, which agreed with the results from other researchers25–27 and was higher than the target ratio (Ag/Pd = 1:3.4), suggesting a silver enrichment at the top surface of the membrane. After thermal treatment (sample c), the Ag/Pd ratio changed from 1:2.5 to 1:3.4, indicating a diffusion of palladium toward the top surface during thermal treatment.…”

Section: Resultssupporting

confidence: 89%

Hydrogen permeance and surface states of Pd‐Ag/ceramic composite membranes

et al. 2006

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Section: Resultssupporting

confidence: 89%

Hydrogen permeance and surface states of Pd‐Ag/ceramic composite membranes

et al. 2006

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“…Surface compositions of different alloys can be predicted by phase diagrams from different empirical models including the ideal solution, real solution, embedded atom [30], or from first principles calculations that have been done by Johansson and coworkers [10,31]. The phase diagrams of the ideal solution model and the first principle studies share similar qualitative features and reasonably predict the experimental surface segregation of AgPd alloys leading to low Pd surface concentrations [32,33].…”

Section: Voltammetry Of Agpd(111) Alloysmentioning

confidence: 92%

“…Results from AgPd alloy surface compositions experiments described in the literature vary considerably for a certain bulk composition due to the different alloy preparation [30,32,33]. Besides on the surface orientation [31,34], the equilibrium surface composition is strongly dependent on the annealing temperature [10,33].…”

Section: Voltammetry Of Agpd(111) Alloysmentioning

confidence: 97%

Hydrogen Evolution Electrocatalysis on AgPd(111) Alloys

Pluntke

Kibler

2011

Electrocatal

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Recent studies on AuPd(111) alloy surfaces display unexpected hydrogen evolution reaction activities-a unique activity of AuPd alloys with surface fractions of~20% Pd was found. We investigated if this phenomenon also occurs with AgPd alloys. We first deposited Pd on a Ru (0001) substrate. After annealing, cyclic voltammetry investigations showed the same characteristics as Pd (111) single crystals. During Ag deposition, cyclic voltammetry experiments disclose underpotential deposition of Ag on the Pd film just as on Pd(111). AgPd alloys were formed by further annealing, and strong enrichment of Ag at the surface is observed. Using this approach, we prepared various bulk compositions at a film thickness of 20 monolayers. Most AgPd alloys show a higher electrocatalytic activity than Ag or Pd alone. The activity trends match those seen with AuPd alloys.

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“…Our measurements of the H 2 –D 2 exchange kinetics across Ag x Pd 1– x composition space occurred in an H 2 -rich environment at atmospheric pressure. While surface enrichment of Ag is reported for Ag x Pd 1– x alloys under vacuum and inert atmospheres due to its lower surface free energy, , inverse surface segregation phenomena have been reported both experimentally and computationally , for Ag x Pd 1– x alloys in H 2 -rich atmospheres. In fact, we have recently shown that a Ag x Pd 1– x CSAF nearly identical to the one studied here could be activated for ethylene hydrogenation by inducing inverse surface segregation phenomena using trace amounts of a spectator species in the reaction mixture .…”

Section: Discussionmentioning

confidence: 99%

H₂–D₂ Exchange Activity and Electronic Structure of Ag_xPd_1–x Alloy Catalysts Spanning Composition Space

Golio,

Sen,

et al. 2024

ACS Catal.

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Many computational studies of catalytic surface reaction kinetics have demonstrated the existence of linear scaling relationships between physical descriptors of catalysts and reaction barriers on their surfaces. In this work, the relationship between catalyst activity, electronic structure, and alloy composition was investigated experimentally using a Ag x Pd 1−x Composition Spread Alloy Film (CSAF) and a multichannel reactor array that allows measurement of steady-state reaction kinetics at 100 alloy compositions simultaneously. Steady-state H 2 −D 2 exchange kinetics were measured at atmospheric pressure on Ag x Pd 1−x catalysts over a temperature range of 333−593 K and a range of inlet H 2 and D 2 partial pressures. X-ray photoelectron spectroscopy (XPS) was used to characterize the CSAF by determining the local surface compositions and the valence band electronic structure at each composition. The valence band photoemission spectra showed that the average energy of the valence band, ε ̅ v , shifts linearly with composition from −6.2 eV for pure Ag to −3.4 eV for pure Pd. At all reaction conditions, the H 2 −D 2 exchange activity was found to be highest on pure Pd and gradually decreased as the alloy was diluted with Ag until no activity was observed for compositions with x Pd < 0.58. Measured H 2 −D 2 exchange rates across the CSAF were fit using the Dual Subsurface Hydrogen (2H′) mechanism to extract estimates for the activation energy barriers to dissociative adsorption, ΔE ads ‡ , associative desorption, ΔE des ‡ , and the surface-to-subsurface diffusion energy, ΔE ss , as a function of alloy composition, x Pd . The 2H′ mechanism predicts ΔE ads ‡ = 0−10 kJ/mol, ΔE des ‡ = 30−65 kJ/mol, and ΔE ss = 20−30 kJ/mol for all alloy compositions with x Pd ≥ 0.64, including for the pure Pd catalyst (i.e., x Pd = 1). For these Pd-rich catalysts, ΔE des ‡ and ΔE ss appeared to increase by ∼5 kJ/mol with decreasing x Pd . However, due to the coupling of kinetic parameters in the 2H′ mechanism, we are unable to exclude the possibility that the kinetic parameters predicted when x Pd ≥ 0.64 are identical to those predicted for pure Pd. This suggests that H 2 −D 2 exchange occurs only on bulk-like Pd domains, presumably due to the strong interactions between H 2 and Pd. In this case, the decrease in catalytic activity with decreasing x Pd can be explained by a reduction in the availability of surface Pd at high Ag compositions.

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Auger electron spectroscopy study of the surface segregation in silver–palladium alloys

Cited by 14 publications

References 35 publications

Hydrogen permeance and surface states of Pd‐Ag/ceramic composite membranes

Hydrogen permeance and surface states of Pd‐Ag/ceramic composite membranes

Hydrogen Evolution Electrocatalysis on AgPd(111) Alloys

H₂–D₂ Exchange Activity and Electronic Structure of Ag_xPd_1–x Alloy Catalysts Spanning Composition Space

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Auger electron spectroscopy study of the surface segregation in silver–palladium alloys

Cited by 14 publications

References 35 publications

Hydrogen permeance and surface states of Pd‐Ag/ceramic composite membranes

Hydrogen permeance and surface states of Pd‐Ag/ceramic composite membranes

Hydrogen Evolution Electrocatalysis on AgPd(111) Alloys

H2–D2 Exchange Activity and Electronic Structure of AgxPd1–x Alloy Catalysts Spanning Composition Space

Contact Info

Product

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About

H₂–D₂ Exchange Activity and Electronic Structure of Ag_xPd_1–x Alloy Catalysts Spanning Composition Space